Transitional user interface for a portion of a display screen



FIG. 1 is a face view of a first image of a transitional user interface for a portion of a display screen, showing my new design; and,

FIG. 2 is a face view of a second image thereof.

The appearance of the transitional user interface sequentially transitions between the images shown in FIGS. 1-2. The process or period in which one image transitions to another image forms no part of the claimed design.

Subject matter shown in broken lines, including text shown in broken lines, forms no part of the claimed design. 

CLAIM The ornamental design for a transitional user interface for a portion of a display screen, as shown and described. 